1. Field of the Invention
The invention relates to a valve mechanism with a variable valve opening cross section, and particularly to such a valve for use as an intake valve or exhaust valve of an internal combustion engine.
2. Prior Art
In internal combustion engines used as driving engine for motor vehicles, a fuel-air mixture is compressed and ignited in the work chamber. The energy produced is converted into mechanical work. It is known for air or the fuel-air mixture to be delivered to the work chamber via valves (inlet valves), and for the products of combustion to be removed from the work chamber via valves (outlet valves). For determining the efficiency of the engine, controlling these valves is of great significance. In particular, the gas exchange in the work chamber is controlled by way of controlling the valves.
In addition to camshaft control, it is also known to employ an electrohydraulic valve control. Electrohydraulic valve control offers the capability of variable or fully variable valve control, making it possible to optimize the gas exchange and thus to enhance the motor efficiency of the engine.
The electrohydraulic valve control includes a hydraulically actuatable control valve, whose control valve piston actuates a valve body of the inlet and outlet valves and leads to a valve seat (valve seat ring) (closure of the valve) or moves away from it (opening of the valve). The control valve can be actuated via a pressure control of a hydraulic medium. The pressure control is effected here via magnet valves incorporated into the hydraulic circuit. To achieve the most optimal possible gas exchanges, the highest possible switching speeds of the control valve are needed. As a result of these high switching speeds, the valve body of the inlet and outlet valves strikes the valve seat ring at high speed. The result is on the one hand noise, and on the other, the partners in the valve suffer relatively high wear.
European Patent Disclosure EP 0 455 761 B1, for instance, has a hydraulic valve control device for an internal combustion engine as its subject. The fundamental technological principle of this embodiment is to displace a motor valve by means of a controlled pressure of a hydraulic fluid. In this embodiment, it is provided that an electronic control unit triggers a magnet valve, which in turn controls the motion of a storage piston, by way of which the stroke of the motor valve is varied.
European Patent Disclosure EP 0 512 698 A1 describes an adjustable valve system for an internal combustion engine. This embodiment is one example of mechanical valve control via cams of a rotating camshaft.
U.S. Pat. No. 4,777,915 has an electromagnetic valve control system for an internal combustion engine as its subject. A similar embodiment of an electromagnetic valve control is known from EP 0 471 614 A1. In these embodiments, the valve is moved back and forth to different positions by electromagnetic force. The electromagnets are disposed inside a housing part of the cylinder head, in two different regions. By the alternating activation of the electromagnets, the valve is moved alternatingly into two terminal positions, corresponding to the opening and closing positions of the valve, respectively. In these terminal positions of the valve, the admission opening for the fuel-air mixture into the combustion chamber is then opened to the widest extent or completely closed.
Another embodiment is known from EP 0 551 271 B1. This embodiment involves a valve mechanism with a plate valve, which is disposed in a passage of an internal combustion engine. The fundamental principle of this embodiment is that the valve plate is divided into two parts; one half of the valve plate executes only a fraction of the stroke executed by the other half of the valve plate.
In these known embodiments for valve control, the major effort of production and assembly of the valve mechanism, because of its complicated design, is especially disadvantageous. This adversely affects the costs for production and assembly. Moreover, in these embodiments, extremely high speeds and strong forces for valve control are necessary, so that an increased vulnerability to malfunction of the valve control from major wear of the parts of the valve mechanism is unavoidable.
The valve mechanism of the invention offers the advantage over the prior art of creating a variable valve opening cross section by simple means. Because a sealing slide is disposed coaxially to the gas exchange valve is acted upon by the force of a coupling spring, and is displaceable axially back and forth by the valve control unit, and because the position of the sealing slide relative to the gas exchange valve in the axial direction is variable by an adjusting unit, which essentially comprises a control slide that is adjustable in the axial direction of the gas exchange valve and is disposed coaxially to the gas exchange valve and to the sealing slide, a valve mechanism is created which has a simple design and which functions reliably and durably. The advantage of the valve mechanism of the invention is in particular that a variable valve opening cross section can be created, and each individual valve can be regulated separately. With the valve mechanism of the invention, the variable valve opening cross section can advantageously be created without high speeds and without strong forces, so that the vulnerability of this valve mechanism to malfunction is very slight. The valve mechanism of the invention can be produced and assembled economically, because of its simple design. The invention advantageously creates a variable valve control by which optimization of the gas exchange and thus an increase in motor efficiency of the engine is possible.
In a preferred feature of the invention, it is provided that the valve control unit is a camshaft.
In a further preferred feature of the invention, it is provided that the gas exchange valve has a rotationally symmetrical basic construction and comprises a valve shaft, on whose lower end a valve plate is disposed.
In a further preferred feature of the invention, it is provided that the valve plate has a conical circumferential face, which forms the sealing seat of the gas exchange valve.
Also in a preferred feature of the invention, it is provided that in the closing position of the valve mechanism, the sealing seat of the gas exchange valve directly contacts both a sealing seat of the sealing slide and a valve seat ring of the cylinder head.
Moreover, in a preferred feature of the invention, it is provided that the sealing slide comprises a bushlike bearing body, which is disposed displaceably axially back and forth inside a guide of the cylinder head.
As a result of these advantageous features of the invention, the delivery of the air, or the fuel-air mixture, can be regulated with great precision, and a high efficiency of the engine can thus be achieved.
Moreover, in a preferred feature of the invention, it is provided that the control slide is connected via a male thread to a corresponding female thread of a gear wheel, surrounding it, that is connected to a rack by which a longitudinal motion can be executed. The particular advantage of this preferred feature of the invention is that with it, a very economical embodiment is created, which advantageously makes it possible for all the inlet and/or outlet valves of an internal combustion engine to be regulated in common via a single component. Triggering a plurality of control slides via this component creates the precondition that allows the control system of the engine to work with only a single sensor.
Moreover, in a preferred feature of the invention, it is provided that associated with the control slide is a securing disk, by way of which the control slide is adjustable in the axial direction. As a result, it is advantageously possible to calibrate the positions of the control slide of an internal combustion engine exactly by compensating for existing tolerances. The individual work cylinders of an engine can be adapted precisely to one another in their function in this simple and advantageous way, and thus an optimal efficiency of the engine can be achieved.